Identification of Armillaria species isolated from bigtooth aspen based on rDNA RFLP analysis

Restriction fragment length polymorphism analysis (RFLP) of the intergenic region (IGR-1) between the 3' end of the 26S ribosomal RNA gene and the 5' end of the 5S rRNA gene was used to identify 39 isolates of Armillaria species collected from live or recently dead bigtooth aspen (Populus grandidentata Michx.) trees and sucker sprouts in the Tioga State Forest, Pennsylvania. The unknown isolates were identified by comparing their restriction fragment patterns with 18 isolates of known Armillaria species common to the northeastern United States. Twenty of the unknown isolates (50%) were identified as either Armillaria gallica or Armillaria calvescens. Eighteen (46%) of the isolates were identified as Armillaria ostoyae. One isolate of Armillaria sinapina was obtained from a recently dead aspen tree. One isolate of Armillaria mellea, considered to be the most divergent of the Armillaria species, was obtained from basidiomes fruiting on a recently dead aspen tree near Berwick, Pennsylvania. In some instances, amplification of DNA was possible by adding mycelial scrapes directly to the polymerase chain reaction (PCR) mix, thus precluding the need for DNA extraction. Advancements in RFLP analysis may offer a method able to provide rapid and precise identification of most North American and European Armillaria isolates.